The present invention relates to an imaging apparatus and an imaging method.
Imaging apparatuses such as an ultrasonic diagnosing apparatus, an X-ray CT apparatus and a magnetic resonance imaging apparatus generate tomograms regarding tomographic planes of a subject. An ultrasonic diagnosing apparatus, for instance, transmits an ultrasonic wave to a subject, generates a tomogram regarding a tomographic plane of the subject on the basis of the ultrasonic wave reflected by the subject and received, and displays the tomogram on a screen.
In an ultrasonic diagnosing apparatus, there are a number of imaging modes including a B mode, a color flow mapping (CFM) mode, and a pulse wave Doppler (PWD) mode. Since this ultrasonic wave diagnosing apparatus can generate and display an image on a real-time basis, it is extensively used in various fields of medicine including fetal examination and cardiac examination in particular.
In an imaging apparatus such as an ultrasonic diagnosing apparatus, a projected image is generated by subjecting tomograms regarding a plurality of tomographic planes in a subject, and the projected image thereby generated is displayed. For instance, it processes maximum intensity projection (MIP) is executed to project the pixels taking on the maximum value in the arrayed direction of the tomographic planes regarding which the plurality of tomograms are generated, and thereby generates an MIP image as the projected image (see Patent Document 1 for example).    [Patent Document 1] Japanese Patent No. 3365929
Incidentally, where an imaging apparatus such as the one referenced above is used, imaging may be carried out after injecting a contrast medium into the subject. For instance, when imaging is to be carried out by using an ultrasonic diagnosing apparatus, after injecting a contrast medium containing micro-bubbles into a blood vessel of the subject in which blood is flowing, the plurality of frames of tomograms are picked up as three-dimensional images. Then, this plurality of frames of tomograms are displayed as moving images consecutively in a time series. This makes it possible to observe how the contrast medium proceeds in the blood vessel, and the observation is used for diagnostic purposes.
However, in the tomogram of each frame, only the part where the contrast medium is positioned in the whole blood vessel at the time of picking up the tomogram of that frame is displayed in high contrast, and other areas are displayed only in low contrast, with the result that when the tomograms of that plurality of frames are to be consecutively displayed as moving images, sometimes it is not easy to keep track of the procession of the contrast medium in the whole blood vessel of the subject. Thus, since the shape of the whole blood in which the contrast medium proceeds is not highly contrastive, it is not easy to accurately keep track of the procession of the contrast medium in the whole blood vessel. This sometimes invites a drop in the efficiency of diagnosis.
In this way, when image diagnosis is to be carried out with an imaging apparatus, trouble of low diagnostic efficiency may occur.